The present invention relates to the field of dental articles. More articularly, the present invention relates to dental articles including post-formable ultilayer optical films including at least one birefringent material.
The use and/or control of light energy is important in many dental procedures, particularly those in which photo-curing adhesives, sealants and dental restorative materials are used. Photo-curing materials preferably cure when exposed to light having a selected wavelength or wavelengths, typically in the visible spectrum.
Photo-curable dental materials are a convenience to the dentist because the curing process can be initiated when desired. For example, a dental filling may be placed in a tooth cavity in contact with a photo-curable dental adhesive and manipulated as needed until the dentist is satisfied that the filling is oriented in its proper position. A source of light including the selected wavelength or wavelengths is then activated to initiate polymerization of the adhesive and securely fix the filling in place. Even in those dental procedures in which photo-curing dental materials are not used, the delivery and control of light is important to allow dental personnel to view the procedures being performed.
Conventional methods of providing reflective optical surfaces in connection with dental articles typically include the use of metal or substrates coated with thin layers of metals. Forming the dental articles including reflective optical surfaces completely of metal is typically expensive and may also suffer from other disadvantages such as increased weight, etc. Metal-coated optical surfaces are typically plastic or other substrates coated with a reflective metallic layer by, e.g., vacuum, vapor or chemical deposition. These coatings suffer from a number of problems including chipping or flaking of the metallic coating, as well as corrosion of the metallic layer.
These problems are exacerbated in many dental applications because the dental articles, including the optical surfaces, that are used in multiple procedures must typically be sterilized between procedures. Sterilization subjects the articles to heat and humidity that can increased the rate of degradation of the optical surfaces. For those dental articles including optical surfaces that may only be metal-coated, the problems of degradation can be even more severe when subjected to sterilization. In many cases, the dental articles including metal-coated optical surfaces may be disposed of after a single use which can increase the cost of the procedures in which those dental articles are used.
When used in connection with photo-curing dental restoratives, another disadvantage of many of the optical surfaces of dental articles includes their inability to selectively reflect or transmit desired wavelengths of light. Many photo-curing dental materials are activated or cured by light in a relatively narrow range of wavelengths, typically in the visible spectrum. Known optical surfaces of dental articles, however, are typically opaque (i.e., they reflect and/or absorb incident light) or they are transmissive for the visible spectrum, thereby preventing or making it difficult to observe the photo-curing dental materials during use without delivering at least some light in the photo-curing wavelengths. As a result, the need to observe the working area can cause at least some photo-curing of the dental materials.
In addition to the above considerations, dental articles often include optical surfaces that are not planar in shape, i.e., the optical surfaces are in the shape of simple or complex curves. Examples include a dental mirror with an optical surface in the shape of a convex surface, a light guide used in connection with the delivery of photo-curing light that employs a curved reflective tube to deliver light from a source to a location within a patient""s mouth, etc.
The present invention provides dental articles including at least one optical surface formed of a multilayer optical film including layers of at least one strain-induced birefringent material. The multilayer optical films included in the dental articles is preferably post-formed into desired non-planar shapes in manners that result in some deformation of the optical stack of the multilayer optical films.
The term xe2x80x9cdental implementsxe2x80x9d as used in connection with the present invention includes devices having at least one optical surface that is designed for use in a dental procedure including, but not limited to: dental mirrors, light guides for use in connection with photo-curing dental materials, matrix bands for use in molding photo-curing dental restoratives, etc. As used in connection with the present invention, the term xe2x80x9cdental articlesxe2x80x9d encompasses devices used in connection with dental procedures. As a result, dental articles includes dental implements designed for use within a patient""s mouth, as well as devices designed to assist dental professionals in dental procedures such as dental operatory lights, room lighting covers, etc. Dental articles also include at least one optical surface. As used herein, the term xe2x80x9coptical surfacexe2x80x9d means a surface that reflects, absorbs, and/or transmits light in a desired manner. In some situations, an optical surface may reflect light of some wavelengths and transmit light of other wavelengths, the optical surface may reflect substantially all incident light, or the optical surface may transmit substantially all incident light, etc.
Among the advantages of the present invention is the ability to improve visibility within a patient""s mouth during dental procedures. By including the highly reflective multilayer optical films according to the present invention, the dental implements are capable of reflecting more of the available light, resulting in improved visibility for dental professionals. In addition, where light is used to photocure dental materials, the improved reflectivity of the multilayer optical films may reduce the curing time, thereby saving time for both the dental professional and the patient.
In one aspect, the present invention provides a dental article including at least one optical surface reflecting light of desired wavelengths, wherein the optical surface includes an optical stack having a plurality of layers, the layers including at least one birefringent polymer and at least one different polymer, wherein the optical stack includes first and second strain-induced index of refraction differentials, the first and second index of refraction differentials being located along first and second perpendicular in-plane axes, and further wherein the thickness of the optical stack varies over the optical surface. The dental articles can be dental implements, e.g., dental mirrors, dental light guides, matrix bands, etc.
In another aspect, the present invention provides a dental article including a lamp cavity having a first optical surface, the first optical surface reflecting light in a first set of desired wavelengths, the lamp cavity further including an opening; and a lens located over at least a portion of the opening in the lamp cavity, the lens having a second optical surface, wherein the second optical surface reflects light in a second set of desired wavelengths; wherein at least one of the first and second optical surfaces includes an optical stack including a plurality of layers, the layers including at least one birefringent polymer and at least one different polymer, wherein the optical stack includes first and second strain-induced index of refraction differentials, the first and second index of refraction differentials being located along first and second perpendicular in-plane axes, and further wherein the thickness of the optical stack varies over the optical surface.
These and other features and advantages of the present invention are discussed below.